WASHINGTON — President Barack Obama said on Wednesday he would name Caroline Kennedy, daughter of the late President John F. Kennedy, as ambassador to Japan, lending the prestige of a storied political dynasty to the relationship with an important Asian ally.

Kennedy, who has a law degree, is president of the John F. Kennedy Library Foundation and chairs an advisory committee at the Institute of Politics at Harvard University. Active in Democratic politics, the 55-year-old was an early and prominent supporter of Obama in his initial quest for the presidency in 2008.

Her appointment is subject to Senate confirmation.

Kennedy’s endorsement, along with that of her uncle, the late Senator Edward Kennedy, gave Obama the stamp of approval of one the most important names in Democratic politics and provided an enormous boost to his candidacy.

Kennedy’s father and another uncle, Robert Kennedy, were felled by assassins’ bullets in the prime of their political careers. Other members of the extended Kennedy clan have gone on to political careers.

Japan is a particularly close and important ally of the United States, and past U.S. ambassadors have been well-known political figures, including former Vice President Walter Mondale.

Tokyo on Thursday welcomed the news, with Chief Cabinet Secretary Yoshihide Suga saying that Kennedy’s lack of experience in diplomacy and dealing with Japan would not be a liability.

“I hear she is very close to President Obama,” he told a news conference. “The ambassador will play an extremely important role in conveying matters directly to the president so we’d like to welcome that.”

Kennedy’s stature will send a strong signal about the value that the United States places on the relationship, said Laurence Leamer, the author of three books about the Kennedy family. If confirmed by the Senate, Kennedy can expect white-hot media attention, he said.

“The Japanese will love her,” Leamer said. “They love the Kennedys. They have this fascination with all things Western, and they’re obsessed with celebrities.”